Preoperative and early postoperative assessment of the internal thoracic artery by transcutaneous duplex ultrasound in coronary artery bypass grafting

We examined internal thoracic artery by transcutaneous duplex ultrasound in 26 patients on four occasions: 4 (±2) days before the operation, and 61 (±8) minutes, 5 days and 53 (±3) days postoperatively. There was dominant systolic flow in preoperative scans. After the operation a characteristic biphasic flow with increased peak diastolic velocity and a decrease in peak systolic/peak diastolic velocity ratio was detected in all patients. The pulsed Doppler spectrum was used to measure peak velocity, time averaged mean velocity and time averaged maximum velocity. Resting internal thoracic artery flows calculated using time averaged mean velocity were 30.9±5.4 ml/min preoperatively, 40.7±6.3 ml/min immediately after surgery, 41.1±8.2 ml/min at 5 days and 40.1±4.9 ml/min at 53 days. There were no significant changes in resting internal thoracic artery flow between early and late postoperative studies. Flow estimates calculated using 0.5×time averaged maximum velocity or time averaged mean velocity showed good agreement. Early postoperative measurements appear to be a good predictor of later resting graft flow.